I used to siphon the stuff out of the bottom of the filter housing. What a mess. Prolly unneeded if there isnt too much sludge. Look at it this way: 99% of the filter housings never got cleaned, just had a new filter cartridge stuffed in. And don't overtighten the filter housing, the rubber gasket will leak. You may have to re-tighten to prevent a slight leak, but its better not to put your back into it the first time you tighten it down. But lube that rubber gasket like you would a normal oil filter ring gasket.
